CODEWITHSUNDEEP
centergetchar
Amin NAIRI
Amin NAIRI

Reputation: 2504

Enter key in a while loop

#include <stdlib.h>
#include <stdio.h>

int main () 
{
    char word[100];

    while (word != "hello") {

        system("clear");

        printf("\nSay hello to me : ");

        scanf(" %s", word);
    }

    printf("congrats, you made it !");

    return 0;
}

In this code : if i enter anything but hello, the loop continue. However, entering the ENTER key will not loop again, it will just add a line.

I read somewhere that using getchar() might help but I'm kinda new to the C developpement and I'm stuck here searching for hours how to make it works.

EDIT 0 :

Removed

while (word != "hello")
char word[100];
scanf(" %s", word);

Added

#include <string.h>
while (strcmp(word, "hello") != 0)
char word[100] = {0}; 
fgets(word, 6, stdin);

EDIT 1 :

I tried to include in my code something like that

fgets(word, 6, NULL);

But it got me a segmentation fault.

**EDIT 2 : **

The correct working input is :

fgets(word, 6, stdin);

So it worked, but adding more than 6 character to the question like :

Say hello to me : hello from the inside

Will just print :

Say hello to me :
Say hello to me :

So I just modified the function like that :

fgets(word, 100, stdin);

But now it will not get me any input to work

Upvotes: 1

Views: 394

Answers (2)

chux
chux

Reputation: 153488

@dbush well answered OP initial concerns.

OP is now using fgets(word, 100, stdin); and types in h e l l o Enter. word[] is then filled with "hello\n" and this does not pass strcmp(word, "hello") != 0.

Solution: strip final '\n'.

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define BUFFER_SIZE 100

int main() {
  char word[BUFFER_SIZE] = { 0 };

  while (strcmp(word, "hello") != 0) {
    system("clear");
    printf("\nSay hello to me : ");
    // insure buffered output is flushed
    fflush(stdout);

    // Avoid magic numbers, use `sizeof  word`
    // Test if input was received
    if (fgets(word, sizeof word, stdin) == NULL) {
      fprintf(stderr, "\nInput closed\n");
      return 1;
    }

    // lop off potential trailing \n
    word[strcspn(word, "\n")] = '\0';
  }

  printf("congrats, you made it !\n");
  return 0;
}

Upvotes: 0

dbush
dbush

Reputation: 223917

Three things:

You don't need the space in the scanf format string. The %s format specifier already ignores leading whitespace. So instead of " %s" use "%s".

The main problem is word != "hello". That's not how strings are compared. What you're actually doing is comparing the address of word with the address of the string constant "hello". To do a string comparison, use strcmp. If it returns 0, the strings are the same, so your while loop should check for non-zero:

while (strcmp(word,"hello")) {

Be sure to #include <string.h> to get the declaration of strcmp.

Finally, you need to initialize word so that the initial string comparison doesn't invoke undefined behavior by reading uninitialized data:

char word[100] = {0};

Upvotes: 3

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